1. “a-” = “not” “tom-” = “cut” “atom” = “indivisible”
Atomic Theory
“a-” = “not”
“tom-” = “cut”
“atom” = “indivisible”

2. You will need to know the contributions of…
Democritus
Dalton
Rutherford
Thomson
Millikan
Curie
Chadwick

3. You will need to know the contributions of…
Democritus–
coined the term “atom” (uncuttable)
suggested the relationship between the particle and the substance

4. You will need to know the contributions of…
Dalton—modern atomic theory
-all matter is made of atoms
-atoms of one element are identical, atoms of different elements are different
-atoms form compounds in simple whole number ratios
-chemical reactions are rearrangements of atoms, the atoms are not changed
-compounds with different ratios of atoms are different compounds

5. You will need to know the contributions of…
Dalton—modern atomic theory
-all matter is made of atoms
-atoms of one element are identical, atoms of different elements are different
-atoms form compounds in simple whole number ratios
-chemical reactions are rearrangements of atoms, the atoms are not changed
-compounds with different ratios of atoms are different compounds
The law of definite proportions
The law of multiple proportions

6. PS
The mass of a proton is about the same as the mass of a neutron (an electron is about 1/1800th of that mass)
This mass is called an atomic mass unit (1 amu)
It is also called a dalton

7. You will need to know the contributions of…
Rutherford-gold foil experiment
-showed atom is mainly empty space
-mass and (+) charge in the center

8. You will need to know the contributions of…
Thomson—cathode “rays”
= stream of electrons,
-calculated charge/mass ratio of electron

9. You will need to know the contributions of…
Millikan—oil drop experiment
determined the charge (& therefore the mass) of an electron

10. You will need to know the contributions of…
Curie—
-described the process of radioactive decay of atoms

11. You will need to know the contributions of…
Chadwick—
-discovered neutrons
Cloud chamber—the straight track shows that it has no charge

12. Protons, neutrons, electrons
Name Symbol Mass Charge Location
Proton
Neutron
Electron

13. Protons, neutrons, electrons
Name Symbol Mass Charge Location
Proton p 1 amu in nucleus
Neutron n 1 amu in nucleus
Electron e amu -1
(about)
(about)
around nucleus, in electron cloud
(about)

14. Atomic number and mass number
Atomic mass number
# electrons

15. Atomic number and mass number
Atomic number is the number of protons—this determines the element
Atomic mass number = #protons + #neutrons
# electrons = # protons, in an uncharged atom

16. What is an isotope?

17. What is an isotope?
“the same”
“place”

18. What is an isotope?
Same Different

19. What is an isotope? Same Different Element Mass
Atomic number Mass number
# protons # neutrons
# electrons Radioactivity
Ion charge
Chemical properties
(mostly)

20. Nuclide Notation
A nuclide is a nucleus or atom of a specific isotope of an element 39 K 19
This is potassium-39. It has 19 protons (atomic number = 19), making it potassium, and 20 neutrons, making a mass number of 39

21. How many p, n, e- in each? What is the mass number and atomic number?3 He 80
Br-
111
Ag+ 2 35 47 59
Fe+2 40
Ca+2
238 Pu 26 20 94

22. Write the nuclide designation
Proton Neutron Electron
(A)
(B)
(C)
(D)

23. Write the nuclide designation
(B)
(C)
(D) 51
V+2 23 14
N-3 7
123
Te-2 52 87
Sr+2 38

24. What is the atomic number and mass number?
Proton Neutron Electron
(A)
(B)
(C)
(D)

25. Average atomic mass
--A weighted average of the naturally occurring isotopes
Ex: 99.63% N-14 (mass= amu/atom)
.37% N-15 (mass= amu/atom)
Avg= (.9963x14.003) +(.0037x15.000)=

26. Average atomic mass
--A weighted average of the naturally occurring isotopes

27. Average atomic mass
--A weighted average of the naturally occurring isotopes
Ex: 99.63% N-14 (mass= amu/atom)
.37% N-15 (mass= amu/atom)
Avg= (.9963x14.003) +(.0037x15.000)=

28. Average atomic mass
--A weighted average of the naturally occurring isotopes
Ex: 99.63% N-14 (mass= amu/atom)
.37% N-15 (mass= amu/atom)
Avg= (.9963x14.003) +(.0037x15.000)=
= = amu / atom

29. Average atomic mass What is the average atomic mass of carbon:
98.89% C-12 ( amu/atom)
1.11% C-13 ( amu/atom)

30. Average atomic mass What is the average atomic mass of carbon:
98.89% C-12 ( amu/atom)
1.11% C-13 ( amu/atom)
amu/atom

31. How common is Cl-37? Cl-35 has a mass of 34.969 amu/atom
The average atomic mass of chlorine is amu/atom

32. How common is S-34? S-32 has a mass of 31.972 amu/atom
(less common nuclides are ignored)
The average atomic mass of sulfur is amu/atom

33. The greatest conversion of all time!
1 amu X x = 1 gram
atom X x mole
Avogadro’s number!